The objective of the research proposed in this application is to investigate the functional role of membrane bound sialic acid groups in skeletal muscle. Preliminary evidence suggests that the enzyme neuraminidase may be important in mediating the effects of calcium on excitable membranes. The proposed research focuses on an electrophysiological characterization of the effects of neuraminidase on muscle membranes. Membrane potentials and input resistance measurements will be made on enzyme treated muscles and the active properties will be examined by hyperpolarizing cells with current injections in order to be able to elicit action potentials. The effects of alteration of extracellular calcium concentration on these parameters in enzyme treated muscles will be studied. An important part of this study is the continuation of efforts to maximize and thoroughly characterize the degree of purity of neuraminidase by affinity chromatography and appropriate enzyme assays. Related work will involve further electrophysiological characterization of the effects of ruthenium red binding on the muscle cell surface as well as further study of the interaction of calcium and ruthenium red binding to the sarcoplasmic reticulum. The latter experiments will be carried out with sarcoplasmic reticulum isolated from muscle homogenates by differential centrifugation and are designed to determine if calcium and ruthenium red bind independently to different populations of sites. If so, ruthenium red may prove to be an important probe in distinguishing between the roles of the sarcoplasmic reticulum and of mitochondria in the regulation of intracellular calcium levels.